ABSTRACT Osteoporosis is a major cause of disability and morbidity in our population. As many as 10 million Americans have osteoporosis and 34 million more have osteopenia. However, bone mineral density (BMD) assessment does not occur in many Americans when indicated and measure currently requires a separate referral and separate imaging scan to obtain BMD. The result is that only 12% of Americans who are at risk of suffering a hip fracture get BMD assessment and this problem is most likely heightened in ethnic/racial subgroups. Preventive measures (e.g., drugs to inhibit bone loss) cannot be administered in the absence of measurement of BMD. We have created, patented and published a quantitative technique to measure BMD from the thoracic spine using chest CT scans without need of calcium phantom under the patient, effectively opening this up to every chest CT both prospectively and previously acquired. We have validated our method in multiple cohorts with cardiac CT scans, but have not achieved sufficient evaluation to sway guidelines and recommendations for preferred use of DXA scanning. This will require evaluation in epidemiologic studies and outcomes that show CT BMD can predict fractures. CT imaging is very common in persons who meet criteria for osteoporosis screening, and these patients have multiple co-morbidities that may be associated with increased bone risk. Effective strategies to prevent bone loss and/or to treat osteoporosis include calcium and vitamin D, hormone replacement when indicated, calcitonin, and bisphosphonate administration. However, many patients remain undiagnosed until their first fracture because of the lack of recognition of the disease. With an increased awareness by endocrinologists, rheumatologists and primary care physicians, the increased use of preventive strategies, the impact of osteoporosis and subsequent hip fractures on those patients should decrease. This use of CT is not fully validated as we have not established the prevalence of the disease with our methods using CT scans in epidemiologic populations; or that low CT BMD correlates with fractures in this population. We have a cohort of 6,814 adults who underwent serial CT imaging 3-5 times over 15 years in the Multi-Ethnic Study of Atherosclerosis (MESA). Our QCT method will be applied to all visible thoracic levels. We therefore plan to: 1) utilize the 19000+ chest CT scans already performed in MESA; 2) develop prevalence of osteopenia, osteoporosis and vertebral fractures; 3) determine the association between low CT-BMD and presence and incidence of fractures in the DM population, with follow-up approaching 15 years in this population. Measuring BMD on chest CT scans will identify whether they have an increased prevalence of osteoporosis and osteopenia, to justify assessing BMD testing when they undergo CT scans. This can simplify and streamline health care screening by assessing two diseases (BMD and CAD or lung cancer) in one test, already acquired clinically in millions of patients, allowing cost-effective osteoporosis diagnosis.